To create better aids and techniques for orientation and mobility training for visually impaired travelers, it is necessary to understand the spatial knowledge of these travelers. While there is a general assumption that the quality of blind travelers' spatial knowledge about their environments limits their ability to orient and move in those environments, there is little evidence in its support due to the lack of methods available to assess spatial knowledge, orientation, or mobility. In particular, the three-level distinction that has been suggested for blind travelers, among landmark, route, and global spatial layout knowledge, while reasonable, has never been demonstrated empirically or as useful in practice. The goal of this project is the development of measures of spatial knowledge that reflect what blind travelers know about their spatial environments, and that predict how well they can orient and move in those environments, as well as easy to administer and score, with proven reliability, and with a demonstrated validity shown by their relation to blind travelers' actual orientation and mobility within those environments being assessed. The three years of effort in the project are divided evenly into the development and validation of measures of spatial knowledge, and the development and validation of measures of orientation and mobility. Spatial knowledge of a scene will be explored by asking subjects: to draw a map of the scene with its boundaries, routes, landmarks and objects; to locate the objects in the scene with markers; to provide distance estimations among objects; to indicate the directions to the objects in the scene; to construct a model of the scene; and to describe verbally the route and objects in the scene. The assessment of orientation and mobility is based on direct measurement of travel rate and direction toward known objects, accuracy of pointing and travel in defined directions, and cane usage and contact. The validity of all the measures will be assessed by experimental manipulation of scene, familiarity, and travel variables. The final data on all measures will be collected on a common set of subjects so that the covariation among the measures can be examined psychometrically.